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  • Convert args to flat list?

    - by Mark
    I know this is very similar to a few other questions, but I can't quite get this function to work correctly. def flatten(*args): return list(item for iterable in args for item in iterable) The output I'm looking for is: flatten(1) -> [1] flatten(1,[2]) -> [1, 2] flatten([1,[2]]) -> [1, 2] The current function, which I from another SO answer doesn't seem to produce correct results at all: >>> flatten([1,[2]]) [1, [2]] I wrote the following function which seems to work for 0 or 1 levels of nesting, but not deeper: def flatten(*args): output = [] for arg in args: if hasattr(arg, '__iter__'): output += arg else: output += [arg] return output

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  • LINQ-to-SQL - C# - OnValidate()

    - by Mark Comix
    Hello, I have a system with 3 layers and I am using LINQ-to-SQL to persist. I want to validate if the description field of my object is empty. I am using partial classes and the method OnValidate(). If the field is empty, it throws an exception. Is this correct? What do I do after the exception to not close the form, letting the user continue working? Thank you very much Sorry for my poor english

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  • Default Accessor Needed: Custom ConfigurationSection

    - by Mark
    I am totally confused by a simple Microsoft error message. When I run XSD.exe against an assembly that contains a custom ConfigurationSection (which in turn utilizes a custom ConfigurationElement and a custom ConfigurationElementCollection, as well as several ConfigurationProperties), I get the following error message: Error: There was an error processing 'Olbert.Entity.Utils.dll'. There was an error reflecting type 'Olbert.Entity.DatabaseConnection'. You must implement a default accessor on System.Configuration.ConfigurationLockCollection because it inherits from ICollection. Yet the class in question has a default accessor: public object this[int idx] { get { return null; } set { } } I realize the above doesn't do anything, but I don't need to access the element's properties by index. I'm just trying to work around the error message. So what's going on?

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  • iPhone app throwing EXC_BAD_ACCESS with dictionary from contents of file

    - by Mark Szymanski
    I have the code NSArray *paths = [[NSArray alloc] initWithArray:NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES)]; NSString *docsDirectory = [[NSString alloc] initWithString:[paths objectAtIndex:0]]; NSLog(@"This app's documents directory: %@",docsDirectory); NSString *docsDirectoryWithPlist = [[NSString alloc] initWithFormat:@"%@/Stuff.plist", docsDirectory]; BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:docsDirectoryWithPlist isDirectory:NO]; if (fileExists) { chdir([docsDirectory UTF8String]); NSMutableDictionary *readDict = [[NSMutableDictionary alloc] initWithContentsOfFile:@"Stuff.plist"]; in an application's applicationDidFinishLaunching method and whenever it gets to the last line it crashes, throwing EXC_BAD_ACCESS along the way. Thanks in advance!

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  • Update C# Chart using BackgroundWorker

    - by Mark
    I am currently trying to update a chart which is on my form to the background worker using: bwCharter.RunWorkerAsync(chart1); Which runs: private void bcCharter_DoWork(object sender, DoWorkEventArgs e) { System.Windows.Forms.DataVisualization.Charting.Chart chart = null; // Convert e.Argument to chart //.. // Converted.. chart.Series.Clear(); e.Result=chart; setChart(c.chart); } private void setChart(System.Windows.Forms.DataVisualization.Charting.Chart arg) { if (chart1.InvokeRequired) { chart1.Invoke(new MethodInvoker(delegate { setChart(arg); })); return; } chart1 = arg; } However, at the point of clearing the series, an exception is thrown. Basically, I want to do a whole lot more processing after clearing the series, which slows the GUI down completely - so wanted this in another thread. I thought that by passing it as an argument, I should be safe, but apparently not! Interestingly, the chart is on a tab page. I can run this over and over if the tabpage is in the background, but if I run this, look at the chart, hide it again, and re-run, it throws the exception. Obviously, it throws if the chart is in the foreground as well. Can anyone suggest what I can do differently? Thanks!

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  • What is the best algorithm for this array-comparison problem?

    - by mark
    What is the most efficient for speed algorithm to solve the following problem? Given 6 arrays, D1,D2,D3,D4,D5 and D6 each containing 6 numbers like: D1[0] = number D2[0] = number ...... D6[0] = number D1[1] = another number D2[1] = another number .... ..... .... ...... .... D1[5] = yet another number .... ...... .... Given a second array ST1, containing 1 number: ST1[0] = 6 Given a third array ans, containing 6 numbers: ans[0] = 3, ans[1] = 4, ans[2] = 5, ......ans[5] = 8 Using as index for the arrays D1,D2,D3,D4,D5 and D6, the number that goes from 0, to the number stored in ST1[0] minus one, in this example 6, so from 0 to 6-1, compare each res array against each D array My algorithm so far is: I tried to keep everything unlooped as much as possible. EML := ST1[0] //number contained in ST1[0] EML1 := 0 //start index for the arrays D While EML1 < EML if D1[ELM1] = ans[0] goto two if D2[ELM1] = ans[0] goto two if D3[ELM1] = ans[0] goto two if D4[ELM1] = ans[0] goto two if D5[ELM1] = ans[0] goto two if D6[ELM1] = ans[0] goto two ELM1 = ELM1 + 1 return 0 //If the ans[0] number is not found in either D1[0-6], D2[0-6].... D6[0-6] return 0 which will then exclude ans[0-6] numbers two: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[1] goto three if D2[ELM1] = ans[1] goto three if D3[ELM1] = ans[1] goto three if D4[ELM1] = ans[1] goto three if D5[ELM1] = ans[1] goto three if D6[ELM1] = ans[1] goto three ELM1 = ELM1 + 1 return 0 //If the ans[1] number is not found in either D1[0-6], D2[0-6].... D6[0-6] return 0 which will then exclude ans[0-6] numbers three: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[2] goto four if D2[ELM1] = ans[2] goto four if D3[ELM1] = ans[2] goto four if D4[ELM1] = ans[2] goto four if D5[ELM1] = ans[2] goto four if D6[ELM1] = ans[2] goto four ELM1 = ELM1 + 1 return 0 //If the ans[2] number is not found in either D1[0-6], D2[0-6].... D6[0-6] return 0 which will then exclude ans[0-6] numbers four: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[3] goto five if D2[ELM1] = ans[3] goto five if D3[ELM1] = ans[3] goto five if D4[ELM1] = ans[3] goto five if D5[ELM1] = ans[3] goto five if D6[ELM1] = ans[3] goto five ELM1 = ELM1 + 1 return 0 //If the ans[3] number is not found in either D1[0-6], D2[0-6].... D6[0-6] return 0 which will then exclude ans[0-6] numbers five: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[4] goto six if D2[ELM1] = ans[4] goto six if D3[ELM1] = ans[4] goto six if D4[ELM1] = ans[4] goto six if D5[ELM1] = ans[4] goto six if D6[ELM1] = ans[4] goto six ELM1 = ELM1 + 1 return 0 //If the ans[4] number is not found in either D1[0-6], D2[0-6].... D6[0-6] return 0 which will then exclude ans[0-6] numbers six: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[5] return 1 ////If the ans[1] number is not found in either D1[0-6]..... if D2[ELM1] = ans[5] return 1 which will then include ans[0-6] numbers return 1 if D3[ELM1] = ans[5] return 1 if D4[ELM1] = ans[5] return 1 if D5[ELM1] = ans[5] return 1 if D6[ELM1] = ans[5] return 1 ELM1 = ELM1 + 1 return 0 As language of choice, it would be pure c

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  • Is there a predefined enumeration for Month in the .NET library?

    - by Mark Rogers
    I'm looking to see if there is an official enumeration for months in the .net framework. It seems possible to me that there is one, because of how common the use of month is, and because there are other such enumerations in the .net framework. For instance, there is an enumeration for the days in the week, System.DayOfWeek, which includes monday, tuesday, etc.. I'm wondering if there is one for the months in the year, ie. January, February, etc? Does anyone know? Thanks for reading!

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  • uiSlider thumb graphic 'flashes' when dragging uiScrollview on 1st gen 3.1.3

    - by Mark Tompson
    I have added my own thumb to a uiSlider and added a 1px x 1px transparent .png to the tracks (I don't want to see the tracks) (I have also tried setting tracks to nil). My uiSlider is also rotated to vertical. The uiSlider sits over a uiScrollView but is not 'attached' to that view. There are numerous uiLabels 'attached' to this uiScrollView, so they all slide about 'beneath' the uiSlider. It all works fine on 3g and iphone 4, but on my 1g itouch (3.1.3) I get a strange flash from the thumb graphic sometimes when scrolling the uiScrollview!? It does seem to happen when the edge of a uiLabel (on the uiScrollView) passes 'under' the thumb graphic? I have tried everything I can think of...

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  • How can I modify a scalar reference passed to a subroutine reference

    - by Mark
    I have a function to convert documents into different formats, which then calls another function based on the type document. It's pretty straight forward for everything aside from HTML documents which require a bit of cleaning up, and that cleaning up is different based on where it's come from. So I had the idea that I could pass a reference to a subroutine to the convert function so the caller has the opportunity to modify the HTML, kinda like so (I'm not at work so this isn't copy-and-pasted): package Converter; ... sub convert { my ($self, $filename, $coderef) = @_; if ($filename =~ /html?$/i) { $self->_convert_html($filename, $coderef); } } sub _convert_html { my ($self, $filename, $coderef) = @_; my $html = $self->slurp($filename); $coderef->(\$html); #this modifies the html $self->save_to_file($filename, $html); } which is then called by: Converter->new->convert("./whatever.html", sub { s/<html>/<xml>/i }); I've tried a couple of different things along these lines but I keep on getting 'Use of uninitialized value in substitution (s///)'. Is there any way of doing what I'm trying to do? Thanks

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  • Fluent NHibernate/SQL Server 2008 insert query problem

    - by Mark
    Hi all, I'm new to Fluent NHibernate and I'm running into a problem. I have a mapping defined as follows: public PersonMapping() { Id(p => p.Id).GeneratedBy.HiLo("1000"); Map(p => p.FirstName).Not.Nullable().Length(50); Map(p => p.MiddleInitial).Nullable().Length(1); Map(p => p.LastName).Not.Nullable().Length(50); Map(p => p.Suffix).Nullable().Length(3); Map(p => p.SSN).Nullable().Length(11); Map(p => p.BirthDate).Nullable(); Map(p => p.CellPhone).Nullable().Length(12); Map(p => p.HomePhone).Nullable().Length(12); Map(p => p.WorkPhone).Nullable().Length(12); Map(p => p.OtherPhone).Nullable().Length(12); Map(p => p.EmailAddress).Nullable().Length(50); Map(p => p.DriversLicenseNumber).Nullable().Length(50); Component<Address>(p => p.CurrentAddress, m => { m.Map(p => p.Line1, "Line1").Length(50); m.Map(p => p.Line2, "Line2").Length(50); m.Map(p => p.City, "City").Length(50); m.Map(p => p.State, "State").Length(50); m.Map(p => p.Zip, "Zip").Length(2); }); Map(p => p.EyeColor).Nullable().Length(3); Map(p => p.HairColor).Nullable().Length(3); Map(p => p.Gender).Nullable().Length(1); Map(p => p.Height).Nullable(); Map(p => p.Weight).Nullable(); Map(p => p.Race).Nullable().Length(1); Map(p => p.SkinTone).Nullable().Length(3); HasMany(p => p.PriorAddresses).Cascade.All(); } public PreviousAddressMapping() { Table("PriorAddress"); Id(p => p.Id).GeneratedBy.HiLo("1000"); Map(p => p.EndEffectiveDate).Not.Nullable(); Component<Address>(p => p.Address, m => { m.Map(p => p.Line1, "Line1").Length(50); m.Map(p => p.Line2, "Line2").Length(50); m.Map(p => p.City, "City").Length(50); m.Map(p => p.State, "State").Length(50); m.Map(p => p.Zip, "Zip").Length(2); }); } My test is [Test] public void can_correctly_map_Person_with_Addresses() { var myPerson = new Person("Jane", "", "Doe"); var priorAddresses = new[] { new PreviousAddress(ObjectMother.GetAddress1(), DateTime.Parse("05/13/2010")), new PreviousAddress(ObjectMother.GetAddress2(), DateTime.Parse("05/20/2010")) }; new PersistenceSpecification<Person>(Session) .CheckProperty(c => c.FirstName, myPerson.FirstName) .CheckProperty(c => c.LastName, myPerson.LastName) .CheckProperty(c => c.MiddleInitial, myPerson.MiddleInitial) .CheckList(c => c.PriorAddresses, priorAddresses) .VerifyTheMappings(); } GetAddress1() (yeah, horrible name) has Line2 == null The tables seem to be created correctly in sql server 2008, but the test fails with a SQLException "String or binary data would be truncated." When I grab the sql statement in SQL Profiler, I get exec sp_executesql N'INSERT INTO PriorAddress (Line1, Line2, City, State, Zip, EndEffectiveDate, Id) VALUES (@p0, @p1, @p2, @p3, @p4, @p5, @p6)',N'@p0 nvarchar(18),@p1 nvarchar(4000),@p2 nvarchar(10),@p3 nvarchar(2),@p4 nvarchar(5),@p5 datetime,@p6 int',@p0=N'6789 Somewhere Rd.',@p1=NULL,@p2=N'Hot Coffee',@p3=N'MS',@p4=N'09876',@p5='2010-05-13 00:00:00',@p6=1001 Notice the @p1 parameter is being set to nvarchar(4000) and being passed a NULL value. Why is it setting the parameter to nvarchar(4000)? How can I fix it? Thanks!

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  • problem writing xml to file with .net mvc - timeout?

    - by Mark
    Hey, so having an issue with writing out to an xml file. Works fine for single requests via the browser, but when I use something like Charles to perform 5-10 repeated requests concurrently several of them will fail. The trace simply shows a 500 error with no content inside, basically I think they start timing out waiting for write access or something... This method is inside my repository class, have also attempted to have repository instance as a singleton but doesn't appear to make any difference.. Any help would be much appreciated. Cheers public void Add(Request request) { try { XDocument requests; XmlReader xmlReader; using (xmlReader = XmlReader.Create(_requestsFilePath)) { requests = XDocument.Load(xmlReader); XElement xmlRequest = new XElement("request", new XElement("code", request.code), new XElement("date", request.date), new XElement("email", new XCData(request.email)), new XElement("name", new XCData(request.name)), new XElement("recieveOffers", request.recieveOffers) ); requests.Root.Element("requests").Add(xmlRequest); xmlReader.Close(); } requests.Save(_requestsFilePath); } catch (Exception ex) { HttpContext.Current.Trace.Warn("Error writing to file: "+ex); } }

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  • ASP.NET AJAX or jQuery (UpdatePanel/ScriptManager or UFrame/jQuery.ajax)

    - by Mark Redman
    Hi, We use the asp.net UpdatePanel and the ScriptManager/ScriptManagerProxy for ajax related functionality; reducing full page refreshes and calling WCF Services respectively. we also use jQuery and plugins for some parts of the UI. We have had some issues with javascript library related conflicts, but have come across some posts indicating that there is a lot more overhead using the UpdatePanel. I have found some limited reference to UFrame: http://www.codeproject.com/KB/aspnet/uframe.aspx www.codeplex.com/uframe Is this a commercially viable replacement for the asp.net UpdatePanel? We use a ScriptManagerProxy to reference WCF services and easily create and use a proxy to call the various WCF service methods. Would using jQuery ajax be a more efficient solution here? We have got this working well on various browsers but now seem to be getting some security related issues (as seen in FF Firebug: Access to restricted URI denied" code: "1012) which seem to have started since using jQuery a lot more. Is it possible/viable to not use ASP.NET Ajax at all?

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  • How to create refresh statements for TableAdapter objects in Visual Studio?

    - by Mark Wilkins
    I am working on developing an ADO.NET data provider and an associated DDEX provider. I am unable to convince the Visual Studio TableAdapater Configuration Wizard to generate SQL statements to refresh the data table after inserts and updates. It generates the insert and delete statements but will not produce the select statements to do the refresh. The functionality referred to can be accessed by dropping a table from the Server Explorer (inside Visual Studio) onto a DataSet (e.g., DataSet1.xsd). It creates a TableAdapter object and configures SELECT, UPDATE, DELETE, and INSERT statements. If you right click on the TableAdapter object, the context menu has a “Configure” option that starts the “TableAdapter Configuration Wizard”. The first dialog of that wizard has an Advanced Options button, which leads to an option titled “Refresh the data table”. When used with SQL Server tables, that option causes a statement of the form “select field1, field2, …” to be added on to the end of the commands for the TableAdapter’s InsertCommand and UpdateCommand. Do you have any idea what type property or interface might need to be exposed from the DDEX provider (or maybe the ADO.NET data provider) in order to make Visual Studio add those refresh statements to the update/insert commands? The MSDN documentation for the Advanced SQL Generation Options Dialog Box has a note stating, “Refreshing the data table is only supported on databases that support batching of SQL statements.” This seems to imply that a .NET data provider might need to expose some property indicating such behavior is supported. But I cannot find it. Any ideas?

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  • Redirecting from an update action to the referrer of the edit

    - by Mark Westling
    My Rails 2.3 application has a User model and the usual controller actions. The edit form can be reached two ways: when a user edits his own profile from the home page, or when an admin user edits someone else's profile from users collection. What I'd like to do is have the update action redirect back to the referred of the edit action, not the update action. If I do a simple redirect_to(:back) within update, it goes back to the edit form -- not good. One solution is to forget entirely about referrers and redirect based on the current_user and the updated user: if they're the same, go back to the home page, else go to the users collection page. This will break if I ever add a third path to the edit form. It's doubtful I'll ever do this but I'd prefer a solution that's not so brittle. Another solution is to store the referrer of edit form in a hidden field and then redirect to this value from inside the update action. This doesn't feel quite right, though I can't explain why. Are there any better approaches? Or, should I stop worrying and go with one of the two I've mentioned?

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  • Representing geographical points/polygons in Python/Django

    - by Cornflake
    I'm building a website in Django, and I want one of my datatypes to be a geographical polygon. I want to mark points on a map (say, in Google Maps) and then store the resulting polygon in the database. Is there any way to do it that will save me the work of typing all the longitudes and latitudes manually? I guess I'm looking both for a geographical library for Python, and for a special website that will let me mark points on the map and save them in a standard format. Thanks!

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  • Simple XML over http web service

    - by Mark
    I have a simple html service, developed in django. You enter your name - it posts this, and returns a value (male/female). I need to ofer this as a web service. I have no idea where to start. I want to accept a xml request, and provide an xml response - thats it. Can anyone give ma any pointers - Googling it is difficult when you dont know what your searching for.

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  • Java and gstreamer-java initialisation error

    - by Mark
    I am building a small app which will play streaming audio from the internet in java (mainly internet radio stations). I have decided to use the gstreamer-java library for the sound, which uses JNA. I would like to include a check in the code, to see whether the gstreamer library has been initialised. When I have left the "Gst.init()" code out (to mimic when the library has not been initialised correctly), the application throws out the following messages: (process:21888): GLib-GObject-CRITICAL **: /build/buildd/glib2.0-2.22.3/gobject/gtype.c:2458: initialization assertion failed, use IA__g_type_init() prior to this function (process:21888): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed The app calls the gstreamer-java library. The error messages appear but the thread continues to run, hogging the CPU. Is there any way to catch the error or to add a check to prevent it from happening? An alternative would be to put the "Gst.init()" in the main class, but I am not sure if this would always guarantee the gstreamer library is initialised.

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  • Native functions throw UnsatisfiedLinkError in custom view, despite working in main activity

    - by Mark Ingram
    For some reason I can only call native functions from my main activity and not any custom views that I've created. Here is an example file (I followed a tutorial, but renamed the classes http://mindtherobot.com/blog/452/android-beginners-ndk-setup-step-by-step/) See the usage of the native function "getNewString". package com.example.native; import android.app.Activity; import android.app.AlertDialog; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Canvas; import android.os.Bundle; import android.view.View; public class NativeTestActivity extends Activity { static { System.loadLibrary("nativeTest"); } private native String getNewString(); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); this.setContentView(new BitmapView(this)); String hello = getNewString(); // This line works fine new AlertDialog.Builder(this).setMessage(hello).show(); } } class BitmapView extends View { static { System.loadLibrary("nativeTest"); } private native String getNewString(); public BitmapView(Context context) { super(context); String hello = getNewString(); // This line throws the UnsatisfiedLinkError new AlertDialog.Builder(this.getContext()).setMessage(hello).show(); } } How can I call native functions in my custom views? I've built the application as an Android 2.2 app. I'm running the application on my HTC Desire. I have the latest SDK (9) and latest NDK (r5).

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  • SQL Design: representing a default value with overrides?

    - by Mark Harrison
    I need a sparse table which contains a set of "override" values for another table. I also need to specify the default value for the items overridden. For example, if the default value is 17, then foo,bar,baz will have the values 17,21,17: table "things" table "xvalue" name stuff name xval ---- ----- ---- ---- foo ... bar 21 bar ... baz ... If I don't care about a FK from xvalue.name - things.name, I could simply put a "DEFAULT" name: table "xvalue" name xval ---- ---- DEFAULT 17 bar 21 But I like having a FK. I could have a separate default table, but it seems odd to have 2x the number of tables. table "xvalue_default" xval ---- 17 table "xvalue" name xval ---- ---- bar 21 I could have a "defaults table" tablename attributename defaultvalue xvalue xval 17 but then I run into type issues on defaultvalue. My operations guys prefer as compact a representation as possible, so they can most easily see the "diff" or deviations from the default. What's the best way to represent this, including the default value? This will be for Oracle 10.2 if that makes a difference.

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  • Turning Floats into Their Closest (UTF-8 Character) Fraction.

    - by Mark Tomlin
    I want to take any real number, and return the closest number, with the closest fraction as available in the UTF-8 character set, appropriate. 0/4 = 0.00 = # < .125 1/4 = 0.25 = ¼ # > .125 & < .375 2/4 = 0.50 = ½ # > .375 & < .625 3/4 = 0.75 = ¾ # > .625 & < .875 4/4 = 1.00 = # > .875 I made this function to do that task: function displayFraction($realNumber) { if (!is_float($realNumber)) { return $realNumber; } list($number, $decimal) = explode('.', $realNumber); $decimal = '.' . $decimal; switch($decimal) { case $decimal < 0.125: return $number; case $decimal > 0.125 && $decimal < 0.375: return $number . '¼'; # 188 ¼ &#188; case $decimal > 0.375 && $decimal < 0.625: return $number . '½'; # 189 ½ &#189; case $decimal > 0.625 && $decimal < 0.875: return $number . '¾'; # 190 ¾ &#190; case $decimal < 0.875: return ++$number; } } What are the better / diffrent way to do this? echo displayFraction(3.1) . PHP_EOL; # Outputs: 3 echo displayFraction(3.141593) . PHP_EOL; # Outputs: 3¼ echo displayFraction(3.267432) . PHP_EOL; # Outputs: 3¼ echo displayFraction(3.38) . PHP_EOL; # Outputs: 3½ Expand my mind!

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  • Custom language - FOR loop in a clojure interpeter?

    - by Mark
    I have a basic interpreter in clojure. Now i need to implement for (initialisation; finish-test; loop-update) { statements } Implement a similar for-loop for the interpreted language. The pattern will be: (for variable-declarations end-test loop-update do statement) The variable-declarations will set up initial values for variables.The end-test returns a boolean, and the loop will end if end-test returns false. The statement is interpreted followed by the loop-update for each pass of the loop. Examples of use are: (run ’(for ((i 0)) (< i 10) (set i (+ 1 i)) do (println i))) (run ’(for ((i 0) (j 0)) (< i 10) (seq (set i (+ 1 i)) (set j (+ j (* 2 i)))) do (println j))) inside my interpreter. I will attach my interpreter code I got so far. Any help is appreciated. Interpreter (declare interpret make-env) ;; needed as language terms call out to 'interpret' (def do-trace false) ;; change to 'true' to show calls to 'interpret' ;; simple utilities (def third ; return third item in a list (fn [a-list] (second (rest a-list)))) (def fourth ; return fourth item in a list (fn [a-list] (third (rest a-list)))) (def run ; make it easy to test the interpreter (fn [e] (println "Processing: " e) (println "=> " (interpret e (make-env))))) ;; for the environment (def make-env (fn [] '())) (def add-var (fn [env var val] (cons (list var val) env))) (def lookup-var (fn [env var] (cond (empty? env) 'error (= (first (first env)) var) (second (first env)) :else (lookup-var (rest env) var)))) ;; for terms in language ;; -- define numbers (def is-number? (fn [expn] (number? expn))) (def interpret-number (fn [expn env] expn)) ;; -- define symbols (def is-symbol? (fn [expn] (symbol? expn))) (def interpret-symbol (fn [expn env] (lookup-var env expn))) ;; -- define boolean (def is-boolean? (fn [expn] (or (= expn 'true) (= expn 'false)))) (def interpret-boolean (fn [expn env] expn)) ;; -- define functions (def is-function? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'lambda (first expn))))) (def interpret-function ; keep function definitions as they are written (fn [expn env] expn)) ;; -- define addition (def is-plus? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '+ (first expn))))) (def interpret-plus (fn [expn env] (+ (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define subtraction (def is-minus? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '- (first expn))))) (def interpret-minus (fn [expn env] (- (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define multiplication (def is-times? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '* (first expn))))) (def interpret-times (fn [expn env] (* (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define division (def is-divides? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '/ (first expn))))) (def interpret-divides (fn [expn env] (/ (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define equals test (def is-equals? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '= (first expn))))) (def interpret-equals (fn [expn env] (= (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define greater-than test (def is-greater-than? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '> (first expn))))) (def interpret-greater-than (fn [expn env] (> (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define not (def is-not? (fn [expn] (and (list? expn) (= 2 (count expn)) (= 'not (first expn))))) (def interpret-not (fn [expn env] (not (interpret (second expn) env)))) ;; -- define or (def is-or? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'or (first expn))))) (def interpret-or (fn [expn env] (or (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define and (def is-and? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'and (first expn))))) (def interpret-and (fn [expn env] (and (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define print (def is-print? (fn [expn] (and (list? expn) (= 2 (count expn)) (= 'println (first expn))))) (def interpret-print (fn [expn env] (println (interpret (second expn) env)))) ;; -- define with (def is-with? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'with (first expn))))) (def interpret-with (fn [expn env] (interpret (third expn) (add-var env (first (second expn)) (interpret (second (second expn)) env))))) ;; -- define if (def is-if? (fn [expn] (and (list? expn) (= 4 (count expn)) (= 'if (first expn))))) (def interpret-if (fn [expn env] (cond (interpret (second expn) env) (interpret (third expn) env) :else (interpret (fourth expn) env)))) ;; -- define function-application (def is-function-application? (fn [expn env] (and (list? expn) (= 2 (count expn)) (is-function? (interpret (first expn) env))))) (def interpret-function-application (fn [expn env] (let [function (interpret (first expn) env)] (interpret (third function) (add-var env (first (second function)) (interpret (second expn) env)))))) ;; the interpreter itself (def interpret (fn [expn env] (cond do-trace (println "Interpret is processing: " expn)) (cond ; basic values (is-number? expn) (interpret-number expn env) (is-symbol? expn) (interpret-symbol expn env) (is-boolean? expn) (interpret-boolean expn env) (is-function? expn) (interpret-function expn env) ; built-in functions (is-plus? expn) (interpret-plus expn env) (is-minus? expn) (interpret-minus expn env) (is-times? expn) (interpret-times expn env) (is-divides? expn) (interpret-divides expn env) (is-equals? expn) (interpret-equals expn env) (is-greater-than? expn) (interpret-greater-than expn env) (is-not? expn) (interpret-not expn env) (is-or? expn) (interpret-or expn env) (is-and? expn) (interpret-and expn env) (is-print? expn) (interpret-print expn env) ; special syntax (is-with? expn) (interpret-with expn env) (is-if? expn) (interpret-if expn env) ; functions (is-function-application? expn env) (interpret-function-application expn env) :else 'error))) ;; tests of using environment (println "Environment tests:") (println (add-var (make-env) 'x 1)) (println (add-var (add-var (add-var (make-env) 'x 1) 'y 2) 'x 3)) (println (lookup-var '() 'x)) (println (lookup-var '((x 1)) 'x)) (println (lookup-var '((x 1) (y 2)) 'x)) (println (lookup-var '((x 1) (y 2)) 'y)) (println (lookup-var '((x 3) (y 2) (x 1)) 'x)) ;; examples of using interpreter (println "Interpreter examples:") (run '1) (run '2) (run '(+ 1 2)) (run '(/ (* (+ 4 5) (- 2 4)) 2)) (run '(with (x 1) x)) (run '(with (x 1) (with (y 2) (+ x y)))) (run '(with (x (+ 2 4)) x)) (run 'false) (run '(not false)) (run '(with (x true) (with (y false) (or x y)))) (run '(or (= 3 4) (> 4 3))) (run '(with (x 1) (if (= x 1) 2 3))) (run '(with (x 2) (if (= x 1) 2 3))) (run '((lambda (n) (* 2 n)) 4)) (run '(with (double (lambda (n) (* 2 n))) (double 4))) (run '(with (sum-to (lambda (n) (if (= n 0) 0 (+ n (sum-to (- n 1)))))) (sum-to 100))) (run '(with (x 1) (with (f (lambda (n) (+ n x))) (with (x 2) (println (f 3))))))

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